The spread of Covid-19 misinformation on social media, according to US President Joe Biden, is "killing people."
He was responding to a reporter's question about "platforms like Facebook" allegedly spreading false information about vaccines and the pandemic.
The White House is putting more pressure on social media companies to combat misinformation.
Facebook is taking "aggressive action" to protect public health, according to the company.
Mr. Biden told reporters at the White House on Friday, "They're killing people." "We only have one pandemic, and it's among the unvaccinated."
Officials in the United States have warned that the current spike in Covid-19 deaths and infections is primarily affecting unvaccinated communities.
Jen Psaki, the White House press secretary, said earlier on Friday that Facebook and other platforms were not doing enough to combat vaccine misinformation.
"Obviously, they've taken steps," she explained. "It's obvious that there's a lot more that can be done."
Kevin McAlister, a spokesman for Facebook, said the company would "not be distracted by accusations that aren't supported by facts."
"We've removed over 18 million pieces of Covid misinformation [and] accounts that break these rules on a regular basis," the company said in a separate statement.
Misleading content about the pandemic is still widely available on Facebook, which has been chastised for its moderation.
"There is a clear message that is coming through: this is becoming a pandemic of the unvaccinated," Rochelle Walensky, director of the US public health agency Centers for Disease Control and Prevention (CDC), told reporters earlier on Friday.
Approximately 67.9% of adults in the United States have received one dose of the vaccine, while 59.2% have received all three doses.
Many people in the United States who are eligible for vaccinations are refusing them because they do not trust them.
Anti-vaccine activists on Facebook, YouTube, Instagram, and Twitter had "more than 59 million followers," according to a March report, making them "the largest and most important social media platforms for anti-vaxxers."
In the same month, Facebook, Google, and Twitter CEOs Mark Zuckerberg, Sundar Pichai, and Jack Dorsey were grilled by Congress over disinformation.
Mr. Dorsey assured the senators that Twitter was committed to moderation. Mr. Pichai stated that YouTube is working to remove misleading content and emphasized the company's role in disseminating vaccine information.
It comes after social media platforms admitted to censoring revelations about politically embarrassing emails leaked from Vice President Joe Biden's son's laptop in the run-up to the presidential election last November.
After his father's campaign claimed without evidence that the New York Post report on Hunter Biden's dealings was "disinformation," Twitter and Facebook blocked links to it.